When reading SAE oil grades for multi-weight oils the lower or "w" number refers to the oil at 40C and upper number is at 100C. A common viscosity measurement is centistokes, (cSt). SAE 50 will have a viscosity near 18 cSt at 100C regardless of whether it is a synthetic or not. The Mobil 1 15w-50 will have a viscosity of 125 cSt at 40C. A 20w-50 will be closer to 170 cSt at 40C. The synthetics usually have a wider viscosity index without as much need for modifiers and their performance can shine at temperatures far away from these standards. One thing that needs to be understood is that for loose tolerance engines or those that are worn too much clearance on one side always means less or insufficient clearance on the other side. As such loose engines can actually be more demanding of the oil to keep the parts separated. As important as an oil pressure gauge is it is even more helpful the have an oil temperature gauge. The Water boxer has a wonderful (?) ability to have oil temperatures not follow the coolant temperature, especially at high speeds and loads and the situation gets worse when the crankcase is over filled. It is these high oil temps that cause the loss of oil pressure both from viscosity loss and the case expansion letting the bearings get loose and the pump to lose its ability to pump. The oil can go into thermal run away and this is where we get those thrown rods. If not for this phenomenon the Water boxer would have no problem running with a *w-30 or *w-40 oil. For daily winter driving (to-from work) I use the 0w-40 which works just fine on my red van which is completely stock. For summer and/or long trips I want the 15w-50. Keep in mind that higher viscosity oils have their draw backs. They provide poorer lubrication when cold and they rob power and economy. Dennis -----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Stuart MacMillan Sent: Wednesday, May 29, 2013 12:26 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: oils and gasoline Ahh, these threads are so much fun! Everyone has an opinion and an opportunity to join in. I can't resist. Regarding better mileage with premium gas, if it doesn't contain 10% (it does here in WA, you are fortunate in Canada) you will get about 3% better fuel economy due to the lower energy content of ethanol (ethanol adds oxygen for more complete combustion). Since you are getting more than that, then you probably have some carbon build up that is increasing compression to the point where you get some knock with heavy loads on regular. Regarding synthetic oils and viscosity, the SAE rating is "effective viscosity," not physical viscosity. A 15w-50 synthetic oil is physically thinner than a 15w-50 dino oil, but the chemistry of a synthetic (more long chain molecules of consistent length plus viscosity extenders) offers the same effective viscosity lubrication with higher breakdown temps in a thinner (purer) oil. With its being thinner we can run into low oil pressure issues with some synthetics in our loose WBX engines (the hotter they get the looser). 15w-50 should be fine, but 20w-50 may be needed in worn engines since it is physically thicker than the 15w-50. Run the 5w oils ("mileage boosting" oil for modern cars) and you can have pressure problems at high temps.
Which brings me to my last point. All WBX engines should have an oil
pressure guage! Van Café has a great kit at a great price (I did my
research):
http://www.van-cafe.com/home/van/page_362_263/oil_pressure_gauge_kit.html
Best money and two hours you'll spend.
I had one on my '84 and am installing this one on my '85 this weekend (and
I'll transfer it to the Subaru engine). It didn't keep me from blowing up
my engine, but at least I knew I was on borrowed time:
http://volksweb.relitech.com/21rodbrg.htm
For more fun reading on oil look up "tribology," which is the science of
lubrication. You will learn that two of the best known lubricants are whale
oil and castor oil (Castrol's original formula).
Stuart
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
James Eaton
Sent: Wednesday, May 29, 2013 5:16 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: oils and gasoline
>
> Date: Mon, 27 May 2013 12:57:38 -0500
> From: Jim Felder <jim.felder@GMAIL.COM>
> Subject: Re: Engine Oil Question
>
> I don't think it's better, I think it's very good and moderately
> priced. I know from many thousands of miles of experience that without
> the right oil (of which Castol 20W50 is one) and the right filter, you
> stand a good chance of hearing your waterboxer's oil buzzer go off on
> a hot day of freeway driving.
>
> It has been explained to me by people who are in the business of
> selling oil and in the business of building engines that the
> waterboxer does not have tolerances that would take advantage of the
synthetics' advantages.
> It's like putting high test in the gas tank; it won't hurt the car
> but it won't help it either, and costs more.
>
> Jim
>
Hmmm,
Even back in the '80s, when I had my Rabbit, we were advised that if you
wanted your engine to last you should run synthetic oil, especially if you
ran a lot under adverse or high load conditions. And that was back when
synthetics were all thin, thin, like 0W20. Now that synthetics are the same
weight as regular oils, only with wider range (e.g. 15W50 is the same
thickness as 20W50, except in the cold, where it's thinner for better lube
at start-up), all engines, even those needing heavier oil to cope with high
temperatures, can find a synthetic to do the job.
And I have a contrary observation to your line about premium octane
gasoline; our '91, with 290k km, gets 2-3 mpg more on 91 octane than on 87
octane on the highway. (The owner's manual recommends the use of 91 octane
under hot, high load conditions, which described our camping trips in
eastern Ontario last summer.) A colleague who teaches and researches gas
engine maintenance and repair suggested that the improvement is likely due
to the superior flame front propagation properties of 91 octane under higher
loads, and to the lower alcohol content (apparently in Ontario premium does
not have to have the 5-10% alcohol that regular does).
James
Ottawa, ON
'91 Westfalia Weekender
=
|
Please note - During the past 17 years of operation, several gigabytes of
Vanagon mail messages have been archived. Searching the entire collection
will take up to five minutes to complete. Please be patient!
Return to the archives @ gerry.vanagon.com
The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.
Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.